An integrated circuit generally comprises active components, for example transistors, mutually separated by isolating areas, for example by deep trench isolation (DTI) or shallow trench isolation (STI). Since air is a very good electrical insulator, the isolating trenches are advantageously hollow.
The techniques routinely used to fabricate an integrated circuit including hollow isolating trenches normally include complete production of the hollow isolating trenches before the production of the active devices.
More specifically, according to these known methods, the trench is etched and then its opening is plugged, for example with a conformal coating of an oxide layer. To avoid more or less completely filling the trench in the plugging operation, it is important for the opening of the trench not to be too large. Consequently, only narrow trenches, which present a reduced air volume, can be obtained with these conventional methods.